Truly a good question because it provoked a lot of thought as to which techniques are possible, valid and practical.
I got it "right" (yay!), but after reading the discussion I think the "adding a where clause in ALL inserts" is very dubious, simply because all inserts may not have a where clause. It could be done if there were no INSERT or UPDATE permissions granted on the table and all access is through stored procedures.
Just because you're right doesn't mean everybody else is wrong.